The invention relates to a strand-guiding roll for supporting and guiding cast metal strands in a continuous casting installation, having a central rotatable shaft and having at least one roll shell supported fixed against rotation on this shaft.
Strand-guiding rolls are used in continuous casting installations to support and guide continuously cast metal strands after they emerge from a mold in a strand-guiding stand. They are exposed to high thermal stresses, since the cast metal strands leave the mold at a temperature of over 1000° C. if they are steel strands for example. In the case of relatively thick strands, there is still a pronounced liquid core in the strand, as a result of which ferrostatic forces act on the strand-guiding rolls. In addition, the strand-guiding rolls have to withstand deformation forces from the strand bending. Accordingly, the strand-guiding rolls are usually equipped with internal cooling and are of a robust design suitable for the mechanical stresses. The considerable width of the cast strands requires multiple mounting of the strand-guiding roll and accordingly a multi-part structure.
In conventional continuous casting installations, two basic types of strand-guiding rolls, which differ in terms of their basic structure, are used.
One basic type of strand-guiding rolls comprises a stationary central axle, on which one or more roll shells are rotatably supported by way of sliding or rolling bearing arrangements. Strand-guiding rolls of this type are already known, for example, from DE-A 197 44 077, DE-A 27 45 578, DE-A 38 23 655 and U.S. Pat. No. 4,351,383. On account of the relative movement between individual components of the strand-guiding rolls, it is necessary to provide bearing arrangements which are exposed to thermal stresses and accordingly require protective measures.
A further basic type of strand-guiding rolls avoids the need for bearing arrangements of this type within the rolls and comprises a central rotatable shaft and roll shells mounted fixedly in terms of rotation thereon. An outline representation of a strand-guiding roll of this type is to be found in DE-A 29 35 217.
DE-A 25 52 969 has disclosed a further strand-guiding roll with a multiply mounted continuous shaft, on which individual roll sections are arranged fixed in terms of rotation by a welded joint. An annular space as coolant conduit is formed between the central shaft and the roll sections and is connected to central supply lines. This welded design means that the strand-guiding roll cannot be dismantled, and therefore the roll sections, which are subjected to high thermal and mechanical stresses, cannot be replaced.
WO 93/19874 has disclosed a strand-guiding roll, the roll bodies of which are formed substantially as a single piece. However, it is very complex and expensive to produce the coolant lines passing through the roll body.
WO 02/38972 A1, based on FIGS. 1a and 1b, reports a prior art which involves a strand-guiding roll with a central, multiply mounted shaft and a plurality of roll shells arranged thereon. The entire inner surface of each roll shell bears against the outer surface of the shaft, and is connected to it fixed against rotation by way of a feather key. This strand-guiding roll is internally cooled via a coolant line which runs centrally within the shaft. A strand-guiding roll of this type has the fundamental drawback of a long heat-transfer path from the shell surface to the coolant line. Gaps between the shaft and the roll shell act as an insulator and additionally impede the dissipation of heat from the strand-guiding roll.
Furthermore WO 02/38972 A1 has disclosed a strand-guiding roll with a multiply mounted shaft and roll shells fitted onto it, each roll shell being arranged fixed against rotation on the shaft by means of a feather key. An annular space, which is filled with a material with a high thermal conductivity, is provided between the roll shell and the shaft over part of the longitudinal extent of the roll shell. The dissipation of heat from the strand-guiding roll is effected by internal cooling via a central coolant line which passes through the shaft. Although the thermally conductive filler avoids the barrier action of an air gap between the roll shell and the shaft, the considerable distance between the thermally stressed roll shell surface and the coolant line nevertheless still exists.
Therefore, it is an object of the present invention to avoid the drawbacks of the known prior art and to propose a strand-guiding roll which is able to better cope with the mechanical and thermal stresses which occur as a result of the strand. In particular, the way in which the roll shell is supported on the shaft is to be able to better match the stresses which occur.